where A is in g, a1= -1.229(0.196), a2= 0.277(0.034), a3= -0.00231(0.00062), a4= 6.650(2.612),
σ1= 0.1223(0.0305) (inter-event) and σ = 0.2284(0.0127) (intra-event), where numbers in brackets are
the standard errors of the coefficients.